This invention relates to an image processing apparatus and method and a medium, and more particularly to an image processing apparatus and method and a medium wherein an image of an imaging object is picked up and converted into image data and the image data is compressed.
A digital video camera is being popularized which compresses picked up moving pictures using a compression method such as the MPEG (Moving Picture Experts Group) compression method and records the compressed moving pictures onto a disk or a semiconductor memory.
In the MPEG method, data of a finite difference between fields or frames (in the following description, where there is no particular necessity for identification between a field and a frame, the term xe2x80x9cfieldxe2x80x9d is used commonly for them) which neighbor each other with respect to time is calculated to achieve temporal data compression. Further, pixel data are converted into DCT (Discrete Cosine Transform) coefficients to achieve spatial data compression.
A digital video camera of the type described above additionally has a hand-shaking correction function for correcting image data against hand-shaking, that is, an inadvertent movement of the digital video camera when an image is picked up by a user. Two different methods are conventionally available for hand-shaking correction. According to one of the methods, hand-shaking is detected by means of a sensor built in the digital video camera, and picked up image pixels obtained by a CCD (Charge Coupled Device) unit are parallelly translated relative to an image based on the detected hand-shaking. According to the other method, signals read out from such a CCD unit are delayed with respect to time.
In such compression of image data as described above, the relationship between the compression ratio and the picture quality depends upon two factors including the information amount (redundancy) of image data before compression and the amount of motion. In particular, in such compression that the picture quality deterioration between image data before compression and decoded data obtained by compression processing of the image data is lower than a predetermined level, for example, where small subjects exhibit quick and random motions, the compression ratio of image data is low.
For example, when an image of a person in front of a fountain is picked up, in order to suppress the picture quality deterioration of the entire image, MPEG compression allocates a comparatively great amount of coded data to random and quick motion of water of the fountain on the background, but uses a comparatively small amount of coded data for the representation of the person. Since a comparatively great amount of data is allocated to image data which is low in redundancy or exhibits quick motion, the picture quality of the person who is the main imaging object is deteriorated. Where image data is compressed such that the picture quality deterioration may be lower than a predetermined level as described above, the conventional digital video camera has a subject to be solved in that a high compression ratio cannot be applied to image data which is low in redundancy or exhibits quick motion.
Further, since hand-shaking correction is performed independently of compression processing of image data, the conventional digital video camera has another subject to be solved in that it has a great apparatus scale and requires a high cost as much.
It is an object of the present invention to provide an image processing apparatus and method and a medium wherein, when an image of an imaging object is picked up and converted into image data and the image data is compressed, the data amount can be reduced without deteriorating the picture quality.
In order to attain the object described above, according to an aspect of the present invention, there is provided an image processing apparatus which picks up and converts an image of an imaging object into image data and compresses the image data, comprising image pickup means for picking up an image of an imaging object and converting the image into image data, compression means for compressing the image data and outputting the compressed data, detection means for detecting a data amount of the compressed data, and control means for controlling an optical condition for the image picked up by the image pickup means in response to the data amount of the compressed data detected by the detection means, the compression means compressing the image data obtained by the conversion of the image pickup means based on the optical condition controlled by the control means.
With the image processing apparatus, since an optical condition upon imaging is controlled in response to a data amount, the data amount can be reduced without deteriorating the picture quality.
According to another aspect of the present invention, there is provided an image processing apparatus which picks up an image of an imaging object and converts the image into image data, comprising image pickup means for picking up an image of an imaging object and converting the image into image data, storage means for storing the image data, calculation means for calculating motion vectors of the image data stored in the storage means, compression means for compressing the image data stored in the storage means making use of the motion vectors and outputting the compressed data, detection means for detecting hand-shaking when a user picks up an image of the imaging object making use of the motion vectors, and correction means for correcting the image data against the hand-shaking in response to a result of the detection of the detection means.
With the image processing apparatus, since hand-shaking is detected using motion vectors which are calculated where compression of image data is involved, the necessity for a hand-shaking sensor is eliminated, and consequently, reduction in scale and cost of the apparatus can be realized.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.